Process for the production of allopregnane-3beta, 11beta, 17alpha, 20beta, 21-pentols



Reichsteins sUbStance A.

' invention:

United States Patent F PROCESS FOR THE PRODUCTION OF ALLOPREG- DIANE-3'3, 115,175, 20 ZI-PEN'IOLS Carl Djerassi, Birmingham, Mich., and George Rosenkranz, Mexico City, Mexico, assignors, by mesue as- 'sig'nments, to Syntex S. A., Mexico City, Mexico, a cor- "poration of Mexico NoDr'awing; Application July 30, 1952, Serial No. 301,802 Claims priority, application Mexico August 1, 1951 9 Claims. (Cl. 260-3975) The present invention relates to a novel method for the preparation of cyclopentanophenanthren'e derivatives. More particularly. the present invention relates to a novel process for the reduction of certain "allopregnan compounds having keto groups in at least the 11 and'20 positions in order to prepare therefrom allopregnan-lvfi- 11B, 170a, 20 8, 2l-p entol also known as Reichsteins substance A. The compound just referred to has been iso-.

lated by Reichstein andother investigators fromthe human organism and is therefore a naturally occurring substance. Up to now however, this substancehad not been successfully synthesized.

In the U. S. patentapplication of Pataki and Kaufm-ann, Serial No. 225,460, filed in the United States Patent Ofiice on May 9, 1951 there is disclosed the preparation of 'allopregnan-3fi, 17d, 2l-triol-11, 20-dione (Reichsteins compound D) and/ or its 20 monoacetate. In theU. S. patent application of Pataki and Kaufmann, Serial No.

200,877 filed December 14, 1950 there is disclosed the production of allopregnan-17 a, 21diol 3,11,20-trione and/ or its esters.

It has now been found that, in accordance with present invention that lithium aluminum hydride reduction of the compounds just before referred to results in the preparation of allopregnan-3fl, 11,8, 17a,'20/8, 21-pentol i 'e. In other words it has been discovered that in these compounds and/or their esters the reduction of the 11 keto group and 20 keto group according to this invention results in the proper optical Jisomer i. e. the 11B, 20B hydroxy groups. Further, the

surprising discovery was made that even when there is present three keto groups i. e. at the 3, 11 and 20 position the reduction takes place in the correct stereochemical path to yield'the desired, ,8, ,8, B-isomer.

The, following equation serves to illustrate the present CHaOR OHzOR Reduction I H Lithium Aluminum Hydride V e In the equation R represents hydrogen or an acyl group i. e. the residue of'any acid normally used for the esterification of steroids, as for example,rthe acyl group may be the residue of a lower fatty acid or benzoic acid. In the above equation further, X represents C=O and CHOR and R has the same significance as previously set forth.

The process of the present invention may be practiced in general by dissolving a suitable compound such as a1- lopregnan-lh, 2.1-diol-3,11,20-trion 21-monoacetate in a suitable solvent such as tetrahydrofurane and adding this solution to a similar solution of lithium aluminum hydride in tetrahydrofurane, the mixture is then refluxed for p a short period of time as for example 30 minutes and the excess reagent decomposed, as tor example, with acetone. The reaction mixture is then diluted with water, extracted with a suitable solvent, washed, dried and evaporated to dryness. The residue-is allopregnan +313, 11 3, 170:, 2013, 2l-pentol (Reichsteins substance A), The residue can be purified or in the alternative it may be directly esterified as for example, acetylated with acetic anhydride and pyridine and after suitable purification, as by chromatography and recrystallization, produced the corresponding triacetate of Reichsteinis substance A. j

The followingspecific examples. serve to illustrate but are not intended to limit the present invention:

Example 1 A solution of 1 g. of allopregnan-l7a, 2l-diol-3 11, 20-trione 2l-monoacetate in 100 cc. of tetrahydrofurane was slowly added to a solution of l g. of lithium aluminum hydride in cc. of tetrahydrofurane The mixture was refluxed during 30iminutes and then acetone was added to decompose the excess reagent. The mixture was 'cli: luted with Water (without the addition of acid), extracted with chloroform, washed, dried and evaporatedto dryness. The residue of the pentol (allopregnan-3B, 11/8, 170:, 20s, 21-pentol) was directly acetylated with acetic anhydride and pyridine by heating the solution 1 hour on the steam bath. The product was purified by chromotographing through a column of ethyl acetate washed alumina. 'The fractions eluted with a mixture benzenechloroform (4:6) were combined and the product was recrystallized from acetone-ether to yield 0.48 g. of colorless crystals of the triacetate of allopregnan-3B, 115, 17 a,

20 3, 21 -pentol M. P. 215-216" C. (ot) +66 (acetone), +74 (chloroform).

The starting material for this example can also be the free compound allopregnan-17a, 2l-dial-3, l1, 20-trione instead of the acetate, the same result being obtained.

Example 2 'to decompose the excess reagent and then the mixture was diluted with water (Without the addition of acid). The

product was extracted with chloroform and washed, with. The pentol'alwater, dried and evaporated to dryness. lopregnan-3/3, 11,9, 2018, 21-pentol left as a residue was acetylated by heating one hour on the steam bath with acetic anhydride and pyridine. The product was purified by chromotographing through a column of ethyl acetate washed alumina. The fractions eluted with benzene chloroform (4:6) were combined and crystallized from acetone-ether to yield 0.51 g. of colorless crystalsl We claim:

1. A process-for thep-roduction of a compound of the following formula:

wherein R is selected from the group consisting of hydrogen, a lower fatty acid acylate and .benzoate, which onion wherein R represents the same group previously set forth and X is selected from the group consisting of C=O and CH-OR, to reduction with lithium aluminum hydride.

2.- A process for production of allopregnan-3B, 11,8, 17a, 20B, 21-pentol which comprises reducing allopregnan- 17oz, 21-diol-3,11,20-t1 ione with lithium aluminum hydride. V

i 3; A process for the production of allopregnan-3fi, 11B, 170;, 205, 21-pentol, which comprises reducing a 21 monoester selected from the group consisting of lower fatty acid esters and benzoic acid ester of allopregnan- 17oz, 2l-diol-3, 11, 20-trione with lithium aluminum hydride.

4. The process of claim 3 wherein the ester is an acetate.

5. A process for production of allopregnan-3B, 1119,

:, 205, 21-pe11tol which comprises reducing allopregnan- 313, 17a, 21-triol-11, -20-dione with lithium aluminum hydride.

6. The process for production of allopregnan-3p, 113, 170:, 20,3, 21-pentol which comprises reducing a 21 monoester selected from the group' consisting of lower fatty acid esters and benzoic acid ester of allopregnan-3fi, 17a, 21triol-11, 20-dione with lithium aluminum hydride. I

7. The process of claim 6 wherein the 21 monester is an acetate.

8. A process for the production of allopregnan-3B, 11B, 170:, 20/3, 21-pentol which comprises reducing a 3,21-diester selected from the group consisting of lower fatty acid esters and benzoic acid ester :of allopregnan-3 3, 17a, 2l-triol-11, ZO-dione with lithium aluminum hydride.

9. The process of claim 8 wherein the 3, 2l-diester is a diacetate.

References Cited in the file of this patent UNITED STATES PATENTS 2,541,105 Sarett Feb. 13, 1951 2,576,311 Schlesinger Nov. 27, 1951 2,628,966 Graber Feb. 17, 1953 2,671,095

Levin Mar. 2 1954 

1. A PROCESS FOR THE PRODUCTION OF A COMPOUND OF THE FOLLOWING FORMULA: 